1. Technical Field
The disclosure relates to a monitoring device that monitors a transmission signal, and a light distribution control device that is designed for use in a lamp for a vehicle and that is equipped with the monitoring device.
2. Description of Related Art
A headlamp for a motor vehicle may adopt a light distribution control system in which an actuator for adjusting an optical axis of the lamp and a vehicle ECU (an electronic control unit) that is provided on a body of the motor vehicle are connected to each other by a local interconnect network (an LIN) and light distribution of the lamp is electronically controlled through transmission/reception of a signal between the actuator and the vehicle ECU. For example, there is configured an on-demand system in which an information signal representing a current light distribution state is transmitted from the actuator in accordance with a request from the vehicle ECU and the vehicle ECU transmits a control signal for controlling the actuator based on this transmitted information signal toward the actuator.
In this system, when an abnormality occurs in the information signal that is transmitted from the actuator (hereinafter referred to as a transmission signal), it is difficult to perform light distribution control with accuracy. Therefore, it is preferable to provide the actuator with a monitoring device for monitoring the transmission signal. For example, as described in Japanese Patent Application Publication No. 2008-306456 (JP 2008-306456 A), it is conceivable to monitor whether or not a transmission signal has been normally transmitted, by detecting the transmitted transmission signal as a monitoring signal through echo back and comparing the detected monitoring signal with the transmission signal that has not been transmitted yet.